The present invention relates to a fastener for removably fixing a plurality of plate-like members.
A conventional fastener of this type is described in Japanese Patent Publication No. 55-45765. As shown in FIGS. 27 to 29, the conventional fastener 101 is designed to detachably secure a pair of plate-like members 113 and 114 having mating perforations. The fastener 101 comprises a grommet 102 including a head 103 having an opening 104 therethrough and a pair of spreadable essentially parallel stems 105 extending axially from opposite sides of the opening for insertion through the mating perforations, a head 107 and a shank 108. The shank 108 is provided with cam surfaces 109 mutually engageable with the stems 105 of the grommet 102 on the sides thereof. The shank 108 forms a bolt 106 designed to spread the pair of stems 105 of the grommet 102. The stems 105 of the grommet 102 are provided with a pair of laterally offset yieldable fingers extending inwardly therefrom. The shank 108 is formed with an annular groove 111 engageable with the fingers 110 so as to prevent retraction of the bolt 106 from the grommet 102 once the bolt 106 has been inserted therein. The extremity of the shank 108 is initially connected to the head 103 of the grommet 102 by frangible connecting webs 112.
According to the structure of the conventional fastener as aforementioned, after the bolt 106 is inserted into the grommet 102, and the stems 105 of the grommet 102 are creeped under a spread condition after a long time, the stems 105 are not returned to their original condition irrespective of rotation of the bolt 106. Accordingly, insertion of the grommet into the mating perforations of the plate-like members 113 and 114 is rendered difficult to cause reduction in working efficiency.